On 6-6-2009 19:44, Orchid XP v8 wrote:
>> Again, dunno why US uses 60Hz, but 50Hz is less lethal (ie. you need
>> more current to distract your heart) than 60Hz. This has something to do
>> with 60Hz almost syncing to some multiply of normal, health heartbeat.
>> Don't remember the details (I was told this at school something like 12
>> years ago).
> 
> Well, given that a normal heartbeat ranges from 50 to 150 BPM depending 
> on how much exercise you're doing...
> 
It is not about the rate of the sinus node, which is indeed in that 
range, but about what happens to a muscle if you rapidly stimulate it. 
At 50 and 60 Hz (does not really differ that much, both are lethal) the 
impulses come so rapidly that the tension in the muscle build up to a 
maximum. So all your muscles including your heart are fully contracted.

If you want non lethal AC current you should significantly increase the 
frequency, then by the skin effect the current stay at the surface and 
never reaches the muscles. Standard experiment goes like this: generate 
a very high voltage with a very high frequency so you get arcs of a few 
centimeter. Connect one pole to a volunteer/victim and let the arcs jump 
off his fingers to the other pole. It won't give more tha a prickling 
sensation in the fingers but it looks cool.

It probably would not surprise you that there are good reasons for not 
having high frequency mains power supplies.

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